The present invention relates to a system and method for renovating pipes by removing accretions or build up in the pipes and then coating the pipes with a coating material.
All types of pipes, such as water pipes, gas pipes, sewer pipes, industrial fuel, chemical manufacturing plant pipes, and the like, are susceptible to build up of accretions or scale on the inner surface of the pipe. One of the reasons for this is corrosion or rust of the pipe surface. Another reason for scale build-up is the deposit of accretions from the material flowing through the pipe onto the pipe surface, such as lime or other deposits of solids from water in a water pipe. These accretions lead to a narrowing of the pipe diameter, reducing the throughput, and the formation of pits, ultimately jeopardizing the pipe integrity and leading to premature failure of the pipe system.
Renovating existing pipes will reduce the need for a complete or partial replacement of a piping system. This is of great advantage where pipes are installed below the ground, inside walls, or in shafts. The only thing that needs to be done is to dismount the instruments and devices at each end of the pipe and to mount them again after the pipe is cleaned and coated. Various pipe renovating systems and methods have been proposed in the past. In some cases, compressed air carrying particles of abrasive material is blown through the pipe. Such a method is described, for example, in U.S. Pat. No. 5,924,913 of Naf. The interior of the pipe is subsequently coated with an adhesive resin, such as an epoxy resin, which is also applied by use of compressed air to blow it through the pipe.
Processes using compressed air in this way can only be used on relatively small diameter pipes, and this cleaning technique can easily result in blocking of the pipe, or major leaks in the pipe when weakened after cleaning by constant high pressure. Pipes may not be adequately cleaned by such a method when major frictional resistance occurs in the pipe system.
U.S. Pat. No. 5,924,913 of Reimelt attempts to overcome these problems. In this method, cleaning abrasives are moved back and forth in the pipe by means of an alternating pressure drop. This may be done by alternately applying a vacuum to opposite ends of the pipe, or alternately supplying compressed air to opposite ends of the pipe. However, this technique can also result in blockages. When an abrasive agent is repeatedly moved back and forth, it will gradually become mixed with the accretions removed from the pipe surface, diluting or reducing the cleaning effect.
It is an object of the present invention to provide a new and improved method and apparatus for renovating pipes.
According to one aspect of the present invention, a pipe renovating method is provided, which comprises the steps of:
supplying a mixture of pressurized gas and particles of abrasive material to a first end of a pipe; and
simultaneously applying suction to a second end of the pipe;
whereby the mixture of gas and abrasive material is pumped in at the inlet end and sucked out at the discharge end.
In an exemplary embodiment, the inlet end of the pipe is connected to a compressor and a supply of abrasive material, while the outlet end is connected to a vacuum pump. This has the advantage that increased gas flow is achieved by the combination of pressure at one end of the pipe and vacuum at the other, reducing the risk of blockages and eliminating or reducing the problem of loss of pressure at bends or elbows in the pipe, since the gas is being pulled through such obstructions by the vacuum even though pressure will be lost. The combination of blowing in air or other gas at one end of the pipe and sucking out the gas or air at the other end of the pipe may be called xe2x80x9cvacuum acceleration.xe2x80x9d Even though the pressure at both the intake side and the discharge side may be well below the maximum pressure permitted for safety purposes, the particles and gas can still be transported at high speed throughout the entire pipe or pipe system using this xe2x80x9cpush and pullxe2x80x9d method.
The pipe may be dried prior to the abrasive treatment, by blowing heated air through the pipe. A liquid coating material may be applied to the surface of the pipe after cleaning in a similar manner, simply by replacing the supply of abrasive material with a supply of coating material. The coating material is then conveyed through the pipe by blowing it in at one end and sucking it out at the other end. The pipe may be heated after the cleaning is complete and prior to applying coating material, in order to improve the flow characteristics of the liquid coating. The combination of pressure at the intake end with vacuum applied at the discharge end (push and pull) applies a high air or gas volume and speed, transporting the coating material, such as epoxy, through the pipe quickly and evenly. This eliminates or reduces variations in epoxy distribution, such as uneven thickness or missed areas which can arise when only pressure or only vacuum is used.
According to another aspect of the present invention, a system for renovating of pipes is provided, which comprises a supply of pressurized gas for connection to a first end of a pipe, a supply of abrasive particulate material for mixing with the pressurized gas, and a vacuum pump for connection to a second end of the pipe, whereby the abrasive material is blown into the pipe at one end and sucked out of the pipe at the other end.
An air heater may also be connected between the gas supply and first end of the pipe, and a coating material supply may be provided to replace the abrasive material supply when the pipe has been sufficiently cleaned, so as to coat the interior of the cleaned pipe with a layer of coating material such as epoxy. A filter is provided at the second end of the pipe for filtering the separated accretions from the pipe from the abrasive material.
The pipe renovating system and method of this invention allows pipe systems to be cleaned and coated more effectively than in the past, and also allows pipes of much larger diameter to be cleaned and coated. The combination of push at one end and pull at the other end of the pipe will reduce the effect of fall off of pressure half way along the pipe or at bends or elbows, and will move a larger volume of air at a higher speed through the pipe than would be possible by application of pressure or vacuum alone. This will clean and coat pipes more reliably and uniformly, and reduce the risk of blockages or pipe blow outs.